ENDOCRINE CHAPTER 46 Flashcards
Types of Chemical Messengers
Hormone Regulatory chemical that is secreted into extracellular fluid and carried by the blood Can act at a distance from source Endocrine system Organs and tissues that produce hormones Only targets with receptor can respond
Paracrine regulators do not travel in blood
Allow cells of organ to regulate each other
Pheromones are chemicals released into the environment to communicate among individuals of a single species
Not involved in normal metabolic regulation within an animal
Some neurotransmitters are distributed by the blood and act as a hormone
Norepinephrine coordinates the activity of heart, liver, and blood vessels during stress
Neurons can also secrete a class of hormones called neurohormones that are carried by blood
Antidiuretic hormone is secreted by neurons of the brain
3 Classes of Hormones
Peptides and proteins Glycoproteins Amino acid derivatives Catecholamines Thyroid hormones Melatonin Steroids—made from cholesterol Sex steroids Corticosteroids
Classes of hormones
Hormones may be categorized as: Lipophilic (nonpolar) – fat-soluble Steroid hormones and thyroid hormones Travel on transport proteins in blood Bind to intracellular receptors Tend to act over brief time period Hydrophilic (polar) – water-soluble All other hormones Freely soluble in blood Bind to extracellular receptors Tend to have much longer active period
Paracrine Regulators
Diverse group of fatty acids that are produced in almost every organ
Regulate a variety of functions
Smooth muscle contraction, lung function, labor, and inflammation
Synthesis is inhibited by nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen
Lipophilic Hormones
Lipophilic hormones include the steroid hormones and the thyroid hormones
Also retinoids, or vitamin A
Can enter cells through plasma membrane
Circulate in the blood bound to transport proteins
Dissociate from carrier at target cells
Pass through the cell membrane
Bind to an intracellular receptor, either in the cytoplasm or the nucleus
Hormone-receptor complex binds to hormone response elements in DNA
Regulate gene expression
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Hydrophilic Hormones
Peptide, protein, glycoprotein, and catecholamine hormones
Too large or polar to cross cell membrane
Bind to receptors on plasma membrane
Initiate signal transduction pathways
Activation of protein kinases
Activate or deactivate intracellular proteins by phosphorylation
Production of second messengers
The Pituitary Gland
Also known as the hypophysis Hangs by a stalk from the hypothalamus Consists of two parts Anterior pituitary (adenohypophysis) Appears glandular Posterior pituitary (neurohypophysis) Appears fibrous Different embryonic origins Different hormones
The Posterior Pituitary
Appears fibrous because it contains axons that originate in cell bodies within the hypothalamus and that extend along the stalk of the pituitary as a tract of fibers
Develops from outgrowth of the brain
Stores and releases two hormones
Both are actually produced by neuron cell bodies in the hypothalamus
The Posterior Pituitary
Antidiuretic hormone (ADH)
Peptide hormone that stimulates water reabsorption by the kidney, and thus inhibits diuresis (urine production)
Oxytocin
Like ADH, composed of 9 amino acids
In mammals, it stimulates the milk ejection reflex and uterine contractions during labor, and it regulates reproductive behavior
The Anterior Pituitary
Develops from a pouch of epithelial tissue of the embryo’s mouth Not part of the nervous system Produces at least 7 essential hormones Tropic hormones or tropins Act on other endocrine glands ACTH, TSH, LH, FSH
Peptide hormones
Adrenocorticotropic hormone (ACTH)adrenal cortex
Melanocyte-stimulating hormone (MSH)
Protein hormones
Growth hormone (GH)muscles, bones
Prolactin (PRL)—production of milk
Glycoprotein hormones Thyroid-stimulating hormone (TSH)thyroid gland Luteinizing hormone (LH)ovary and testes Follicle-stimulating hormone (FSH)ovary and testes FSH and LH Function in both men and women Referred to as gonadotropins
Anterior pituitary is controlled by hormones from hypothalamus
Neurons secrete releasing hormones and inhibiting hormones, which diffuse into blood capillaries at the hypothalamus’ base
Each hormone delivered by the hypothalamohypophyseal portal system regulates a specific anterior pituitary hormone
Portal system has 2 capillary beds (not 1)
The hypothalamus and the anterior pituitary are partially controlled by the very hormones whose secretion they stimulate
Negative feedback or feedback inhibition
Acts to maintain relatively constant levels of the target cell hormone
Pituitary gland was referred to as the “master gland”
Hypophysectomy caused a number of deficits
Growth Hormone
Stimulates protein synthesis and growth of muscles and connective tissues
Stimulates cell division in epiphyseal growth plates – elongation of bone
Gigantism vs pituitary dwarfism
Also functions in adults to regulate protein, lipid, and carbohydrate metabolism
Acromegaly
